Yale University Astronomy Department Newsletter Vol. 5 Spring 2014 No. 1 Kenney captures dwarf galaxy in the act of dying Professor Jeff Kenney has found concrete evidence that dwarf galaxies stop forming stars due to the process known as ram pressure stripping. Kenney and his team of researchers have caught the Virgo Cluster galaxy IC3418 in the act of transforming from a dwarf irregular galaxy into a dwarf elliptical galaxy. The metamor- phosis happens as gas is stripped from the galaxy through ram pressure, a forceful wind that is caused by the collision of the gas in the galaxy with the gas in intracluster space. With no gas available for star formation, dwarf elliptical galax- ies are considered “dead.” Therefore, Kenney and his team are witnessing the first clear example of a dwarf galaxy in the act of dying. “We think we’re witnessing a critical stage in the transforma- X-ray image showing hot gas in the Virgo cluster with an enlarged UV image of dwarf galaxy IC3418 sporting tion of a gas-rich dwarf irregular galaxy (SEE DWARF, p. 4) a tail of recently formed stars. J. Kenney and P. Jachym. Massive black holes alive and well in dwarf galaxies Dwarf galaxies may be small, but astronomers now know that they can hold massive black holes. Yale astronomer Marla Geha and collaborators have identified more than 100 dwarf galaxies that show signs of hosting mas- sive black holes, a discovery that challenges the idea that they exist only in much bigger galaxies. “These galaxies are comparable in size to the Magellanic Clouds, dwarf satellite galaxies of the Milky Way,” said Geha, associate professor of astronomy. “Previously, such galaxies were thought to be too small to have such massive black holes.” Dwarf galaxies are small, faint, low-mass galaxies with rela- tively few stars compared with, say, the Milky Way, Earth’s home galaxy. Black holes are points in space where matter is Depicted here is NGC4395, a low mass galaxy with a known packed so densely that light itself cannot escape; massive black central black hole. Image courtesy of the researchers. holes are an extreme form of black hole. (SEE HOLES, p. 4) INSIDE THIS ISSUE Science News 1 Recent Graduates 16 Greetings from the Chair 2 Awards and Honors 18 Department Research Programs and Facilities 6 In Memoriam 19 People 14 Aumni News 20 1 Greetings from the Chair Looking back on the time since the last Newsletter, it is amazing to see how much has been achieved and how much the department continues to evolve. Among the most visible changes is the renovation of the library and the accompanying increased activity on that side of the hallway. Quite often, most of the new desks are occupied by majors, graduate students, postdocs, and the occasional bemused faculty member. The class- room also got a facelift, along with some much needed improvements behind the scenes. Next in line is a renovation of the kitchen and lounge area; the idea is that this becomes a single open space for informal gatherings and discussions. We have maintained a very high level of science activity in the department, in large part owing to our outstanding postdocs and graduate students. Several achievements are highlighted in this Newsletter. We also interact a lot with each other, aided by events such as YODA (Yale Overarching Discussion of Astro), ST@Y (Stellar Tea at Yale), and Galaxy Lunch. It is impressive that we have an event or talk nearly every day of the week, and that these events all have dedicated groups of people who ensure their success. Perhaps inspired by these postdoc- and graduate-student-led activities, the faculty have restarted their Friday Scholarship lunches, where they discuss science or other topics such as teaching, mentoring, and applying for grants. Our computer and telescope facilities continue to be productive, including the twin Keck telescopes which form the back- bone of our private telescope access. We are in the midst of two transitions: we are moving to a more comprehensive and powerful computer cluster, and we are reorienting our 4m-class telescope access. Yale was a founding member of the 3.5m WIYN telescope consortium, but after nearly 24 years of successful use, we found that our scientific priorities had shifted in a different direction. As of April 1, 2014, Yale will no longer be a member of the consortium. Based on the results of a com- prehensive survey of graduate students, postdocs, and faculty, we have shifted our focus in 4m-class science to the Palomar 5m telescope in California, as its instrumentation is an excellent match to our evolving needs. Sadly, we had to say goodbye to Suzanne Tourtellotte this year. Suzanne passed away in June after a long illness. She ded- icated her career to enabling others to experience the Universe, whether through teaching introductory courses or through the planning and execution of observations for the SMARTS consortium. She will be greatly missed by her SMARTS col- leagues, by the staff, and by everyone who knew her. Charles Bailyn wrote a tribute to her in this issue (SEE p. 19). Newsletter Editorial Staff Editor-in-Chief: Pieter van Dokkum Editor: Victoria Misenti Writing: Victoria Misenti Others as credited Design: Victoria Misenti Copy Editor: Emily MacPherson Photography: As credited Please send your comments and news to: Editor, Astronomy Newsletter Yale University P.O. Box 208101 New Haven, CT 06520-8101 [email protected] Palomar 5m telescope with adaptive optics laser. Photo by W. S. Kardel. 2 Arce gets foot in the door with early ALMA research Hector Arce is part of a Yale-Universidad de Chile collabo- optical sources. 2) The elevation of ALMA’s site means that ration in star formation that was awarded coveted time for there is less contamination from the atmosphere. 3) The “Cycle 0” on the new Atacama Large Millimeter/submilli- newer technology of ALMA makes it a better and more sen- meter Array (ALMA) in Chile. Arce has also been awarded sitive facility. time for his “Cycle 1” proposals, but his observations have been delayed due to weather and engineering needs. AL- Arce remarked, “ALMA is like putting on new glasses when MA’s superb sensitivity and resolution have made it pos- you know you need a new prescription. Everything becomes sible for Arce to detect features in the observed outflows of much more clear and you can see the details.” Even though protostars much more clearly than previously. his observations only used 16 of the total of 66 antennas that the telescope array will eventually have, Arce believes that Arce and his team used the ALMA time to discover that the results from his first use of the facility “are clear evidence the outflows of a typical protostar in the Gum Nebula are that once completed, this telescope will revolutionize the moving at greater velocities than previously measured, field of star formation.” which leads to a more dramatic impact of the outflow on the star formation environment than astronomers previously The paper presenting Arce’s ALMA “Cycle 0” observations thought occurred. If the observed source is representative of is titled ALMA Observations of the HH 46/47 Molecular Out- outflows in general, Arce’s research indicates that protostel- flow and it appeared in the September 2013 issue of The As- lar outflows could provide the energy to sustain turbulence trophysical Journal. Co-authors are Diego Mardones of the in star-forming clouds and help in dispersing the gas around University of Chile, Stuartt Corder of ALMA, Guido Garay newly formed stars. of the Universidad de Chile, Alberto Noriega-Crespo of the California Institute of Technology, and Alejandro C. Raga of The ALMA observations additionally allowed Arce’s team Universidad Nacional Autónoma de México. The observa- to discover more about the structure of the outflow launch- tions were supported by funding from the National Science ing mechanism and to find evidence that the outflow and Foundation. disk accretion are both episodic. For ALMA's “Cycle 2,” Arce has collaborated on a number ALMA is superior to previous radio telescopes for several of proposals on a wide range of topics including studying reasons: 1) ALMA is in the Atacama desert—one of the dri- star-forming cores and the early stages of star formation in est places on Earth—so it is relatively free from the water nearby clouds, the impact of outflows from massive proto- vapor that can obstruct radio waves just as clouds obstruct stars on their surroundings, and a survey of protoplanetary disks in the Orion nebula cluster. New Yonsei-Yale Isochrones and models available The Yonsei-Yale (Y2) Isochrones have been developed by a collaboration of researchers at Yale (led by Professor Pierre Demarque) and Yonsei University since 2001 and have re- cently been updated with a new set of stellar tracks and iso- chrones focusing on low mass stars (down to 0.1 Msun). According to Professor Sukyoung Yi of Yonsei University, “Isochrones are currently the best tools for measuring the ages of star clusters and fundamental building blocks for galaxy population synthesis.” Demarque added that “they should be useful to a lot of people, including both stellar population and exoplanet researchers.” The latest Y2 Isochrones are available for download on the Yale website http://www.astro.yale.edu/demarque/yyiso. html. A paper that accompanied the release, which was led by Federica Spada with Demarque, Yong Cheol Kim and Alison Sills, was published in the October 2013 volume of Comparison between models using the new Y2 (in red) and other sets of publicly available tracks and iso- The Astrophysical Journal.